Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$246.41	9.245%	$269.1906	$269.19	$269.20	$269.20
Purchase #2	$180.35	11.396%	$200.9027	$200.90	$200.90	$200.90
Purchase #3	$18.46	10.789%	$20.4516	$20.45	$20.45	$20.50
Purchase #4	$42.39	5.508%	$44.7248	$44.72	$44.70	$44.70
Purchase #5	$186.98	7.116%	$200.2855	$200.29	$200.30	$200.30
Purchase #6	$46.82	6.199%	$49.7224	$49.72	$49.70	$49.70
Purchase #7	$146.99	6.632%	$156.7384	$156.74	$156.75	$156.70
7 purchase totals =	$868.40		$942.0160	$942.01	$942.00	$942.00